The present invention relates to electrical control switching, and it relates, more particularly, to a switching arrangement having an internal latch that is released responsive to an increase in current such as produced by stalling an electric motor.
In automobiles having power windows operated by motors, it is convenient and also a safety feature to be able to activate a window, such as the driver's window, by means of a momentary activation which automatically de-activates itself upon the occurrence of an extreme window position. The extreme position of the window may be either fully opened or completely closed. The momentary activation typically involves setting a switch in a single fleeting operation. The switch then sustains the operation until completion. The switch and possible additional circuitry is made to sense and automatically responds to the occurrence of the completed task by de-activation. Typically, the sensing is done by monitoring the current draw of the motor used to provide the mechanical work which stalls upon completing the task.
Various arrangements have been devised to provide this feature, but they all suffer from one or more of the following drawbacks. Although a number of conventional implementations recognize the advantage of the control switch somehow sensing the motor current directly, most of these conventional implementations use electromagnetic means in a single control switch involving coils. Such a multipurpose switch is rather complex and they are costly to manufacture. Furthermore, another conventional approach involves additional sensing devices such as limit switches which also requires additional wiring in the harnesses which is expensive to implement. The use of timing arrangements aside from the high costs involved doesn't appear feasible and also may reduce the operational life expectancy of the driving motor. In any case, it is desirable to implement this operational feature in a separate compact arrangement of low complexity and low cost instead of incorporating it directly within the normal control switch.
It would be highly desirable to provide a low cost device for this control function which is reliable and safe. With the increasing amount of remote and powered controls in automobiles, such a device may be used for power sun roofs, power seats, trunk latches, electric antennas, and the like in vehicles. Further even in other completely different applications, such a control device may be used to advantage.